1. Field of the Invention
The present invention relates generally to crank and slide presses for manufacturing metal containers. More particularly, the present invention relates to a redraw carriage apparatus that may be easily and rapidly removed, replaced, and aligned.
2. Description of the Related Art
Crank and slide presses are used for punching, shearing, drawing, and redrawing operations in manufacturing articles from metallic sheets or rolls of metallic strip material. In general, a crank and slide press includes a crank that is mounted for rotary motion, an electric motor that is connected to the crank that imparts rotary motion thereto, a connecting rod that is attached to the crank, and mechanism for changing motion from the connecting rod to rectilinear reciprocating motion. A more detailed description of crank and slide presses is given by Maytag in U.S. Pat. No. 3,696,657, issued Oct. 10, 1972.
One specific use for a crank and slide press is in the production of beverage cans. A redraw cup is drawn from a coiled strip by a first crank and slide press, and then the redraw cup is redrawn on a second crank and slide press forcing the redraw cup through a tool pack subassembly that includes a redraw die and plurality of ironing dies.
In the highly competitive container industry, a container must be made with the absolute minimum of material, which means that the finished container must have extremely thin walls. It should be apparent that the use of extremely thin walls of the finished containers places stringent concentricity requirements upon the walls of the container and upon such parts of the tooling as the redraw punch and redraw die.
Further, because of the competitiveness of the container industry, the speed of the press must be maximized and downtime of the press must be minimized. As should be apparent, maximizing speed and minimizing down time are inherently opposite, because higher speeds impose higher stresses on the machinery and cause higher wear rates.
In the redraw operation, a tool pack subassembly, with the redraw die thereof, is mounted circumferentially around the longitudinal axis wherein the body maker ram is reciprocated; a redraw punch is attached to the body maker ram and is reciprocated towards, into, and through the tool pack subassembly including both the redraw die and the ironing dies thereof; and the redraw punch is withdrawn from the tool pack subassembly and all of the parts thereof.
A redraw cup is positioned against the redraw die and is resiliently held against the redraw die by a redraw sleeve, the redraw sleeve is attached to a redraw carriage, and the redraw carriage is reciprocated toward and away from the redraw die.
The redraw sleeve serves two functions. One function of the redraw sleeve is to assure concentricity between the redraw cup and the redraw die. The other function of the redraw sleeve is to provide resilient clamping between a clamping face of the redraw sleeve, the redraw cup, and the redraw die, thereby preventing wrinkling of the metal as the redraw cup is redrawn through the redraw die.
In the prior art, such as typified by the aforesaid patent to Maytag, the redraw carriage has been actuated toward the redraw die by a cam that is attached to the crank of the press, and by a cam follower mechanism that receives motion from the cam and then transfers this motion to the carriage. It has been customary to use an air cylinder to maintain the cam follower in contact with the cam and to actuate the redraw carriage away from the redraw die.
Various methods have been used to attach the redraw carriage to the crank and slide press. One of these methods has been to mount the redraw carriage on guide rails and to use rollers both on top of and underneath the guide rails to position and align the redraw carriage, as shown in the aforementioned patent to Maytag. However, this method of mounting has required high maintenance to maintain alignment, and considerable time has been required to remove, replace, and realign the redraw carriage.
Grims et al., U.S. Pat. No. 4,807,459, which was issued on Feb. 28, 1989, shows a device in which the redraw carriage is slidably mounted to a pair of spaced-apart guide rods, and these guide rods are secured to the tool pack subassembly. The primary weakness of this design is that removal of the tool pack subassembly automatically means removal of, or at least removal of alignment of, the redraw carriage as the tool pack subassembly is removed and the guide rods are pulled away from, and out of, the redraw carriage.
In contrast to the prior art, the present invention provides a redraw carriage subassembly which can be rapidly removed, replaced, and realigned without disturbing the tool pack subassembly. Removal consists of removing four cap screws and moving the carriage subassembly transversely away from the longitudinal axis of the machine. Replacement consists of moving a new or rebuilt subassembly transversely to the longitudinal axis of the body maker ram, loosely securing the redraw carriage subassembly to the frame of the machine with four cap screws, homing the redraw carriage subassembly against one frame member by the use of two homing screws, and tightening the four cap screws.
In a first aspect of the present invention, redraw carriage apparatus is provided for use in a can-making machine that includes a frame having a pair of spaced-apart frame members, a redraw die being disposed around a longitudinal axis in a plane intermediate of the frame members, a body maker ram having both a first end proximal to the redraw die and a second end that is attached to a ram carriage distal from the redraw die, a redraw punch being attached to the body maker ram proximal to the first end thereof and being reciprocable along the longitudinal axis with the redraw punch entering into and withdrawing from the redraw die, which redraw carriage apparatus comprises a first guide rod being disposed intermediate of the redraw die and the ram carriage, being disposed parallel to the longitudinal axis, and being attached to one of the frame members; a second guide rod being disposed parallel to the first guide rod and being attached to the frame; a redraw carriage being disposed around the longitudinal axis, and being slidably mounted to the guide rod; means, including means for forcing the one guide rod transversely with respect to the one frame member, for aligning one of the guide rods with respect to the one frame member; and means, including the redraw carriage being slidably mounted to the guide rods, for aligning the other of the guide rods with respect to the one frame member.
In a second aspect of the present invention, redraw carriage apparatus is provided for use in a can-making machine that includes a frame having a pair of spaced-apart frame members, a redraw die being disposed around a longitudinal axis in a plane intermediate of the frame members, a body maker ram having both a first end proximal to the redraw die and a second end that is attached to a ram carriage distal from the redraw die, a redraw punch being attached to the body maker ram proximal to the first end thereof and being reciprocable along the longitudinal axis with the redraw punch entering into and withdrawing from the redraw die, which redraw carriage apparatus comprises first and second guide rods each having first and second ends, both being disposed parallel to the longitudinal axis, and being spaced apart; a redraw carriage being disposed around the longitudinal axis, and being slidably mounted to the guide rods; a first support frame being attached to the one frame member, and having first and second spaced-apart support posts each with a bore that supportingly receives one of the ends of the first guide rod; a second support frame being attached to the other of the frame members, and having first and second spaced-apart support posts each with a bore that supportingly receives one of the ends of the second guide rod; means, including means for loosening the attachment of the support frames from the frame members, for removing the redraw carriage without removing the redraw carriage from the guide rods and without removing the redraw die; means, including a pair of homing screws, for aligning the first support frame with respect to the one frame member; and means, including the redraw carriage being slidably mounted to the guide rods, for aligning the second support frames with respect to the one frame member.
In a third aspect of the present invention, a method is provided for using a metal working crank and slide press that includes a frame having a pair of spaced-apart frame members, a tool pack subassembly including a redraw die that is disposed around a longitudinal axis in a plane intermediate of the frame members, a body maker ram having a first end proximal to the redraw die and a second end that is attached to a ram carriage distal from the redraw die and being reciprocable along the longitudinal axis, a redraw punch being attached to the body maker ram proximal to the first end thereof and both entering into and withdrawing from the redraw die, and a redraw carriage subassembly, including a redraw carriage, that is disposed intermediate of the tool pack subassembly and the ram carriage, which method comprises slidably inserting first and second guide rods into the redraw carriage to form the redraw carriage subassembly; attaching the first guide rod to one of the frame members; attaching the second guide rod to the frame; homing the first guide rod with respect to the one frame member; and using the redraw carriage to align the second guide rod with respect to the one guide rod.